SSD storage stands for Solid State Drive. SSDs are non-volatile long term storage for data. SSDs use flash memory. SSDs use a grid of electrical cells to read data and contain nomoving parts. These grids are separated into sections called “pages,” and these pages are where data is stored. Pages are clumped together to form “blocks.” SSDs can only write to empty pages in a block. In HDDs, data can be written to any location on the plate at any time, and that means that data can be easily overwritten. SSDs can’t directly overwrite data in individual pages. They can only write data to empty pages in a block. When enough pages in a block are marked as unused, the SSD commits the entire block’s worth of data to memory, erases the entire block, then re-commits the data from memory back to the block while leaving the unused pages blank. Note that erasing a block doesn’t necessarily mean the data is fully gone. Since an SSD can’t directly overwrite an individual page, every time you want to write new data from that point on, the SSD needs to:
Flash memory can only sustain a finite number of writes before it dies. As an SSD is used, the electrical charges within each of its data cells must be periodically reset. The electrical resistance of each cell increases slightly with every reset, which increases the voltage necessary to write into that cell. Eventually, the required voltage becomes so high that the particular cell becomes impossible to write to.